Study of the irradiation-induced alpha ->omega phase transformation in titanium: kinetics and mechanism

An atomic-crystallographic mechanism is proposed for the alpha --> omega tr ansformation during irradiation. The mechanism is based on the propagation of a localized displacement wave of the [100](alpha) close-packed rows. Fro m the phonon dispersion curves along (010)(alpha), the displacement wave is decomposed into two transverse optical phonons and one transverse acoustic phonon. The proposed mechanism accounts for the omega morphology and can e xplain the presence of (2 (1) over bar 0)(alpha) planes of diffuse intensit y in reciprocal space. The. kinetic of the transformation was followed by i n-situ length and electrical resistance measurements. An analytical model b ased on the proposed mechanism enabled us to fit the experimental curves. F inally the kinetic results were compared with those obtained previously for the transformation occurring under an applied static pressure.